[GitHub] [daffodil] scholarsmate commented on a diff in pull request #876: Add Daffodil Developer Guide

[GitBox <gi...@apache.org>]

scholarsmate commented on code in PR #876:
URL: https://github.com/apache/daffodil/pull/876#discussion_r1023075074


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DEVELOP.md:
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+<!--
+  Licensed to the Apache Software Foundation (ASF) under one or more
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+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+
+# Daffodil Developer Guide
+
+This guide is for a software engineer who wants to develop Daffodil
+code.  This guide will help you become familiar with DFDL schemas,
+DFDL processors, and Daffodil development including its code style,
+code workflow, development environment, directory organization,
+documentation, and tests.
+
+## DFDL
+
+The [Data Format Description
+Language](https://en.wikipedia.org/wiki/Data_Format_Description_Language)
+(DFDL) is a language used to describe almost all data formats both
+logically and physically.  DFDL is not a data format or a procedural
+language; rather, it is a data modeling language based on a subset of
+XML Schema annotated with DFDL properties describing the
+representation and layout of each element of the schema inside a
+native text or binary data format.  A DFDL schema allows data to be
+converted between its native data format (physical representation,
+also called a text or binary file) and a DFDL information set (logical
+representation, also called an infoset) such as an XML document, EXI
+document, JSON document, SAX callbacks, or several document object
+model APIs in memory (JDOM, Scala Node, W3C DOM).  When you have a
+DFDL schema for a native data format, you can pick whichever infoset
+type is easiest for you or your application to use and tell a DFDL
+processor to read ("parse") a text or binary file from its native data
+format to that infoset type.  You or your application can do whatever
+you need to do with the infoset and then you can use the same DFDL
+schema and DFDL processor to write ("unparse") the infoset back to its
+native text or binary file format again, completing a round trip from
+native data to infoset to native data again.
+
+Using DFDL avoids inventing a completely new data modeling language,
+avoids writing any parsing and serialization code (with all the bugs
+that normally arise from implementing such code procedurally), and
+makes it much easier to convert any native data format to an infoset,
+operate on the infoset, and convert an infoset back to its native data
+format again.
+
+To learn more about DFDL, you can watch two short
+[videos](https://community.ibm.com/community/user/integration/viewdocument/get-started-with-the-data-format-de)
+put together by Steve Hanson, co-chair of the DFDL working group, read
+a
+[slideshow](https://www.slideshare.net/mbeckerle/dfdl-and-apache-daffodil-overview-from-owl-cyber-defense)
+written by Mike Beckerle, co-chair of the DFDL working group, or go
+through some [tutorials](http://www.xfront.com/DFDL/) written by Roger
+Costello, chair of the DFTVL working group (Data Format Transformation
+and Validation Language, a future not-yet-defined language to specify
+policies for cross-domain system devices).

Review Comment:
   I would replace "cross-domain system devices" with "Cross-Domain Solution (CDS) devices".



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